A study of nonlinear harmonic distortion in a balanced armature actuator with asymmetrical magnetic flux

• The study establishes transduction equations for a balanced armature actuator to analyze the nonlinear harmonic distortion caused by asymmetrical magnetic flux.
• Asymmetrical magnetic flux results in simultaneous even- and odd-order harmonic distortions.
• By adjusting the eccentric position of the armature and the cross-sectional area of the air gap between the permanent magnets and armature, the nonlinear harmonic distortion can be reduced.
• Appropriate nonlinear parameters can reduce the nonlinear harmonic distortion of the balanced armature actuator significantly.

This study investigates the nonlinear harmonic distortion caused by the asymmetrical magnetic flux in a balanced armature actuator (BAA). To account for asymmetrical magnetic flux, a set of transduction equations with nonlinear parameters for a BAA is first established. Next, the nonlinear transduction equations are solved correctly and with great efficiency by utilizing the hybrid spline difference method. Unlike symmetrical magnetic flux that leads to odd-order harmonic distortion only, analysis results demonstrate that asymmetrical magnetic flux in the electromagnetic field leads to the simultaneous appearance of even- and odd-order harmonic distortions. Meanwhile, the present study also indicates that the nonlinear harmonic distortion of the BAA can be reduced by adjusting the eccentric position of the armature and the cross-sectional area of the air gap between the permanent magnets and armature. Results presented herein provide valuable information not only on the desired design of a BAA but also on the diagnosis and improvement of its performance.